The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Many automatic motor vehicle transmissions include a plurality of gear arrangements, interconnecting members, shafts, and torque transmitting mechanisms, among other mechanical members. The various torque transmitting mechanisms are employed to selectively transmit torque from one rotating member to another or from a rotating member to a stationary member. Typical examples of torque transmitting mechanisms may include synchronizers, dog clutches, and multiple friction disc clutches and brakes. A multiple disc clutch or brake, for example, may be used to connect a member of a planetary gear set such as a ring gear with the transmission housing, thus changing the output of that particular planetary gear set.
Such torque transmitting mechanisms can make clacking noises or other noises because they are often used to connect or disconnect transmission gears, shafts, or other parts that are rotating at different speeds or to connect a part that is rotating with a stationary part. For example, clutch plate teeth can vibrate within a spline of an inner hub or an outer housing and make corresponding noises. Such noises were traditionally masked by the sounds created by an internal combustion engine. However, when an electric motor is being used in a hybrid or electric vehicle, noises from the motor vehicle powertrain, such as from torque transmitting mechanisms, gear, or clutch plates, become easier to hear. These noises are often deemed undesirable from a customer's point-of-view.
One way to reduce noise from within the vehicle powertrain is to form the components from cast iron. Cast iron is known for having a relatively high damping capacity; however, cast iron components are heavy, and the general trend in automotive technology is to lighten vehicle components to achieve greater fuel economy. In addition, cast iron may have other drawbacks, such as potential for cracking. Polymers are another material having a high damping capacity; however, polymers are typically not strong enough to carry the torque loads transmitted through a vehicle powertrain, and in addition, they may not withstand the harsh fluids, heat, and other environmental factors within a vehicle powertrain.
Accordingly, there exists a need to dampen sounds created by a motor vehicle transmission, while continuing to strive toward the goal of creating light-weight and fuel-efficient vehicles that are amenable to large-scale manufacturing.